Search Results (183 total)

Using a data sample of 24.5×10⁶ ψ(2S) the reactions ψ(2S)→γχ_cJ, χ_cJ→γγ have been studied for the first time to determine the two-photon widths of the χ_cJ states of charmonium in their decay into two photons. The measured quantities are B(ψ(2S)→γχ_c0)×B(χ_c0→γγ)=(2.17±0.32±0.10)×10^-5 and B(ψ(2S)→γχ_c2)×B(χ_c2→γγ)=(2.68±0.28±0.15)×10^-5. Using values for B(ψ(2S)→γχ_c0,c2) and Γ(χ_c0,c2) from the literature the two-photon widths are derived to be Γ_γγ(χ_c0)=(2.36±0.35±0.22)  keV, Γ_γγ(χ_c2)=(0.66±0.07±0.06)  keV, and R≡Γ_γγ(χ_c2)/Γ_γγ(χ_c0)=0.278±0.050±0.036. The importance of the measurement of R is emphasized. For the forbidden transition, χ_c1→γγ, an upper limit of Γ_γγ(χ_c1)<0.03  keV is established.

In this Letter, we describe a search for lepton flavor violation (LFV) in the bottomonium system. We search for leptonic decays Υ(nS)→μτ (n=1, 2, and 3) using the data collected with the CLEO III detector. We identify the τ lepton using its leptonic decay ν_τν̅ _ee and utilize multidimensional likelihood fitting with probability density function shapes measured from independent data samples. We report our estimates of 95% C.L. upper limits on LFV branching fractions of Υ mesons. We interpret our results in terms of the exclusion plot for the energy scale of a hypothetical new interaction versus its effective LFV coupling in the framework of effective field theory.

Using Υ(2S) and Υ(3S) data collected with the CLEO III detector we have searched for decays of χ_bJ to final states with open charm. We fully reconstruct D⁰ mesons with p_D⁰>2.5  GeV/c in three decay modes (K^-π⁺, K^-π⁺π⁰, and K^-π^-π⁺π⁺) in coincidence with radiative transition photons that tag the production of one of the χ_bJ(nP) states. Significant signals are obtained for the two J=1 states. Recent nonrelativistic QCD (NRQCD) calculations of χ_bJ(nP)→cc̅ X depend on one nonperturbative parameter per χ_bJ triplet. The extrapolation from the observed D⁰X rate over a limited momentum range to a full cc̅ X rate also depends on these same parameters. Using our data to fit for these parameters, we extract results which agree well with NRQCD predictions, confirming the expectation that charm production is largest for the J=1 states. In particular, for J=1, our results are consistent with cc̅ g accounting for about one-quarter of all hadronic decays.

We study exclusive χ_c0,1,2 decays to four-hadron final states involving two charged and two neutral hadrons: π⁺π^-π⁰π⁰, K⁺K^-π⁰π⁰, pp̅ π⁰π⁰, K⁺K^-ηπ⁰, and K^±π^∓K⁰π⁰. The χ_c states are produced in radiative decays of 3.08×10⁶ ψ(2S) resonance decays and observed in the CLEO detector. We also measure the largest substructure contributions to the modes π⁺π^-π⁰π⁰ and K^±π^∓K⁰π⁰.

We report the first observation of Υ(2S)→ηΥ(1S), with a branching fraction B=(2.1_-0.6^+0.7(stat)±0.3(syst))×10^-4 and a statistical significance 5.3σ. Data were acquired with the CLEO III detector at the CESR e⁺e^- symmetric collider. This is the first process observed involving a b-quark spin flip. For related transitions, 90% confidence limits in units of 10^-4 are B(Υ(2S)→π⁰Υ(1S))<1.8, B(Υ(3S)→ηΥ(1S))<1.8, B(Υ(3S)→π⁰Υ(1S))<0.7, and B(Υ(3S)→π⁰Υ(2S))<5.1.

A precision measurement of the mass of the h_c(¹P₁) state of charmonium has been made using a sample of 24.5×10⁶ ψ(2S) events produced in e⁺e^- annihilation at the Cornell Electron Storage Ring (CESR). The reaction used was ψ(2S)→π⁰h_c, π⁰→γγ, h_c→γη_c, and the reaction products were detected in the CLEO-c detector. Data have been analyzed both for the inclusive reaction and for the exclusive reactions in which η_c decays are reconstructed in 15 hadronic decay channels. Consistent results are obtained in the two analyses. The averaged results of the present measurements are M(h_c)=3525.28±  0.19(stat.)±0.12(syst.)  MeV, and B(ψ(2S)→π⁰h_c)×B(h_c→γη_c)=(4.19±0.32±0.45)×10^-4. Using the ³P_J centroid mass, ΔM_hf(1P)≡⟨M(χ_cJ)⟩-M(h_c)=+0.02±0.19±0.13  MeV.

We measure the mass of the η^′ meson using ψ(2S)→π⁺π^-J/ψ, J/ψ→γη^′ events acquired with the CLEO-c detector operating at the CESR e⁺e^- collider. Using three decay modes, η^′→ρ⁰γ, η^′→π⁺π^-η with η→γγ, and η^′→π⁺π^-η with η→π⁺π^-π⁰, we find M_η^′=957.793±0.054±0.036  MeV, in which the uncertainties are statistical and systematic, respectively. This result is consistent with but substantially more precise than the current world average.

We search for a non-SM-like CP-odd Higgs boson (a₁⁰) decaying to τ⁺τ^- or μ⁺μ^- in radiative decays of the Υ(1S). No significant signal is found, and upper limits on the product branching ratios are set. Our τ⁺τ^- results are almost 2 orders of magnitude more stringent than previous upper limits. Our data provide no evidence for a Higgs state with a mass of 214 MeV decaying to μ⁺μ^-, previously proposed as an explanation for 3 Σ⁺→pμ⁺μ^- events observed by the HyperCP experiment. Our results constrain NMSSM models.

We measure the branching ratio of the purely leptonic decay of the D⁺ meson with unprecedented precision as B(D⁺→μ⁺ν)=(3.82±0.32±0.09)×10^-4, using 818  pb^-1 of data taken on the ψ(3770) resonance with the CLEO-c detector at the CESR collider. We use this determination to derive a value for the pseudoscalar decay constant f_D⁺, combining with measurements of the D⁺ lifetime and assuming |V_cd|=|V_us|. We find f_D⁺=(205.8±8.5±2.5)  MeV. The decay rate asymmetry Γ(D⁺→μ⁺ν)-Γ(D^-→μ^-ν̅ ) / Γ(D⁺→μ⁺ν)+Γ(D^-→μ^-ν̅ )=0.08±0.08, consistent with no CP violation. We also set 90% confidence level upper limits on B(D⁺→τ⁺ν)<1.2×10^-3 and B(D⁺→e⁺ν)<8.8×10^-6.

We perform a Dalitz plot analysis of D⁺→K^-π⁺π⁺ decay with the CLEO-c data set of 572  pb^-1 of e⁺e^- collisions accumulated at the ψ(3770). This corresponds to 1.6×10⁶ D⁺D^- pairs from which we select 140 793 candidate events with a small background of 1.1%. We compare our results with previous measurements using the isobar model. We modify the isobar model with an improved description of some of the contributing resonances and get better agreement with our data. We also consider a quasi-model-independent approach and measure the magnitude and phase of the contributing Kπ S wave in the range of invariant masses from the threshold to the maximum in this decay. This gives an improved description of our data over the isobar model. Finally we allow for an isospin-two π⁺π⁺ S wave contribution and find that adding this to both the isobar model and the quasi-model-independent approach gives the best description of our data.

We report the first observation of the decay J/ψ→3γ. The signal has a statistical significance of 6σ and corresponds to a branching fraction of B(J/ψ→3γ)=(1.2±0.3±0.2)×10^-5, in which the errors are statistical and systematic, respectively. The measurement uses ψ(2S)→π⁺π^-J/ψ events acquired with the CLEO-c detector operating at the CESR e⁺e^- collider.

Using data taken with the CLEO-c detector at the Cornell Electron Storage Ring, we have investigated the direct-photon momentum spectrum in the decay J/ψ(1S)→γgg, via the “tagged” process: e⁺e^-→ψ(2S); ψ(2S)→J/ψπ⁺π^-; J/ψ→γ+X. Including contributions from two-body radiative decay processes, we find the ratio of the inclusive direct-photon branching fraction to that of the dominant three-gluon branching fraction [R_γ=B(ggγ)/B(ggg)] to be R_γ=0.137±0.001±0.016±0.004, where the errors shown are statistical, systematic, and the model-dependent uncertainty related to the extrapolation to zero photon energy. The shape of the scaled photon energy spectrum in J/ψ→ggγ is observed to be very similar to that of Υ→ggγ. The R_γ value obtained is roughly consistent with that expected by a simple quark-charge scaling [R_γ∼(q_c/q_b)²] of the value determined at the Υ(1S), but somewhat higher than the value expected from the running of the strong coupling constant.

Using a sample of 2.59×10⁷ ψ(2S) decays collected by the CLEO-c detector, we present results of a study of χ_cJ (J=0, 1, 2) decays into baryon-antibaryon final states. We present the world’s most precise measurements of the χ_cJ→pp̅ and χ_cJ→ΛΛ̅ branching fractions, and the first measurements of χ_c0 decays to other hyperons. These results illuminate the decay mechanism of the χ_c states.

We exploit the quantum coherence between pair-produced D⁰ and D̅ ⁰ in ψ(3770) decays to study charm mixing, which is characterized by the parameters x and y, and to make a first determination of the relative strong phase δ between doubly Cabibbo-suppressed D⁰→K⁺π^- and Cabibbo-favored D̅ ⁰→K⁺π^-. We analyze a sample of 1.0×10⁶ D⁰D̅ ⁰ pairs from 281  pb^-1 of e⁺e^- collision data collected with the CLEO-c detector at E_cm=3.77  GeV. By combining CLEO-c measurements with branching fraction input and time-integrated measurements of R_M≡(x²+y²)/2 and R_WS≡Γ(D⁰→K⁺π^-)/Γ(D̅ ⁰→K⁺π^-) from other experiments, we find cos⁡δ=1.03_-0.17^+0.31±0.06, where the uncertainties are statistical and systematic, respectively. In addition, by further including external measurements of charm mixing parameters, we obtain an alternate measurement of cos⁡δ=1.10±0.35±0.07, as well as xsin⁡δ=(4.4_-1.8^+2.7±2.9)×10^-3 and δ=(22_-12-11⁺¹¹⁺⁹)°.

We report determination of branching fractions for the decays ψ(2S)→h+J/ψ, where h=any, π⁺π^-, π⁰π⁰, η, π⁰, and γγ through χ_c0,1,2. These measurements use 27M ψ(2S) decays produced in e⁺e^- collision data collected with the CLEO detector. The resulting branching fractions and ratios thereof improve upon previously achieved precision in all cases, and in combination with other measurements permit determination of B(χ_cJ→γJ/ψ) and B(ψ(2S)→light hadrons).

By using 1.8×10⁶ DD̅ pairs, we have measured B(D⁰→π^-e⁺ν_e)=0.299(11)(9)%, B(D⁺→π⁰e⁺ν_e)=0.373(22)(13)%, B(D⁰→K^-e⁺ν_e)=3.56(3)(9)%, and B(D⁺→K̅ ⁰e⁺ν_e)=8.53(13)(23)% and have studied the q² dependence of the form factors. By combining our results with recent lattice calculations, we obtain |V_cd|=0.217(9)(4)(23) and |V_cs|=1.015(10)(11)(106).

Using a sample of 1.8 million DD̅ mesons collected at the ψ(3770) with the CLEO-c detector, we study the semileptonic decays D⁰→π^-e⁺ν_e, D⁺→π⁰e⁺ν_e, D⁰→K^-e⁺ν_e, and D⁺→K̅ ⁰e⁺ν_e. For the total branching fractions we find B(D⁰→π^-e⁺ν_e)=0.299(11)(9)%, B(D⁺→π⁰e⁺ν_e)=0.373(22)(13)%, B(D⁰→K^-e⁺ν_e)=3.56(3)(9)%, and B(D⁺→K̅ ⁰e⁺ν_e)=8.53(13)(23)%, where the first error is statistical and the second systematic. In addition, form factors are studied through fits to the partial branching fractions obtained in five q² ranges. By combining our results with recent unquenched lattice calculations, we obtain |V_cd|=0.217(9)(4)(23) and |V_cs|=1.015(10)(11)(106), where the final error is theoretical.

We exploit the quantum coherence between pair-produced D⁰ and D̅ ⁰ in ψ(3770) decays to study charm mixing, which is characterized by the parameters x and y, and to make a first determination of the relative strong phase δ between D⁰→K⁺π^- and D̅ ⁰→K⁺π^-. Using 281  pb^-1 of e⁺e^- collision data collected with the CLEO-c detector at E_cm=3.77  GeV, as well as branching fraction input and time-integrated measurements of R_M≡(x²+y²)/2 and R_WS≡Γ(D⁰→K⁺π^-)/Γ(D̅ ⁰→K⁺π^-) from other experiments, we find cos⁡δ=1.03_-0.17^+0.31±0.06, where the uncertainties are statistical and systematic, respectively. By further including other mixing parameter measurements, we obtain an alternate measurement of cos⁡δ=1.10±0.35±0.07, as well as xsin⁡δ=(4.4_-1.8^+2.7±2.9)×10^-3 and δ=(22_-12-11⁺¹¹⁺⁹)°.

Using 281  pb^-1 of data collected with the CLEO-c detector, we present new measurements of Cabibbo-suppressed decays of D⁰ and D⁺ mesons to η and η^′ final states. We make first observations of D⁰→η^′π⁰, ηη, ηη^′, and ηπ⁺π^-, and find evidence for D⁺→ηπ⁺π⁰, D⁺→η^′π⁺π⁰, and D⁰→η^′π⁺π^-. We also report on improved measurements of D⁰→ηπ⁰, D⁺→ηπ⁺, and D⁺→η^′π⁺. Using the measured two-body Cabibbo-suppressed decays, we extract amplitudes for specific flavor topologies and compare them to those from Cabibbo-favored decays.

Using 281  pb^-1 of data collected with the CLEO-c detector at the ψ(3770) resonance, we have studied Cabibbo-suppressed decays of D mesons to final states with two kaons. We present results for the absolute branching fractions of the modes D⁰→K⁺K^-, D⁰→K_S⁰K_S⁰, and D⁺→K⁺K_S⁰. We measure B(D⁰→K⁺K^-)=(4.08±0.08±0.09)×10^-3, B(D⁰→K_S⁰K_S⁰)=(1.46±0.32±0.09)×10^-4, and B(D⁺→K⁺K_S⁰)=(3.14±0.09±0.08)×10^-3. We also determine the ratio B(D⁰→K⁺K^-)/B(D⁰→π⁺π^-)=2.89±0.05±0.06. For each measurement, the first uncertainty is statistical and the second uncertainty is systematic.

We investigate the influence of magnetic fields upon the dynamics of, and resulting gravitational waves from, a binary neutron-star merger in full general relativity coupled to ideal magnetohydrodynamics. We consider two merger scenarios: one where the stars have aligned poloidal magnetic fields and one without. Both mergers result in a strongly differentially rotating object. In comparison to the nonmagnetized scenario, the aligned magnetic fields delay the full merger of the stars. During and after merger we observe phenomena driven by the magnetic field, including Kelvin-Helmholtz instabilities in shear layers, winding of the field lines, and transition from poloidal to toroidal magnetic fields. These effects not only mediate the production of electromagnetic radiation, but also can have a strong influence on the gravitational waves. Thus, there are promising prospects for studying such systems with both types of waves.

Using e⁺e^-→D_s^*-D_s⁺ data collected near the peak D_s production energy, E_cm=4170  MeV, with the CLEO-c detector, we present the first observation of the decay D_s⁺→pn̅ . We measure a branching fraction B(D_s⁺→pn̅ )=(1.30±0.36_-0.16^+0.12)×10^-3. This is the first observation of a charmed meson decaying into a baryon-antibaryon final state.

The branching fractions of D_s^± meson decays serve to normalize many measurements of processes involving charm quarks. Using 298  pb^-1 of e⁺e^- collisions recorded at a center of mass energy of 4.17 GeV, we determine absolute branching fractions for eight D_s^± decays with a double tag technique. In particular we determine the branching fraction B(D_s⁺→K^-K⁺π⁺)=(5.50±0.23±0.16)%, where the uncertainties are statistical and systematic, respectively. We also provide partial branching fractions for kinematic subsets of the K^-K⁺π⁺ decay mode.

Using a sample of tagged D_s⁺ decays collected near the D_s^*±D_s^∓ peak production energy in e⁺e^- collisions with the CLEO-c detector, we study the leptonic decay D_s⁺→τ⁺ν_τ via the decay channel τ⁺→e⁺ν_eν̅ _τ. We measure B(D_s⁺→τ⁺ν_τ)=(6.17±0.71±0.34)%, where the first error is statistical and the second systematic. Combining this result with our measurements of D_s⁺→μ⁺ν_μ and D_s⁺→τ⁺ν_τ (via τ⁺→π⁺ν̅ _τ), we determine f_Ds=(274±10±5)  MeV.

We measured the angle- and polarization-resolved reflection and photoluminescence spectra of ZnO inverse opals. Significant enhancement of spontaneous emission is observed. The enhanced emission not only has good directionality but can also be linearly polarized. A detailed theoretical analysis and numerical simulation reveal that such enhancement is caused by the abnormal dispersion of a high-order photonic band. The frozen mode at a stationary inflection point of a dispersion curve can strongly modify the intensity, directionality, and polarization of spontaneous emission.